Genetic Screening for Novel Regulators of Immune Checkpoint Molecules

Enhanced Antitumor Immunity Through T Cell Activation with Optimized Tandem Double-OX40L mRNAs

Purpose

The tumor immune microenvironment (TIME) is often dysfunctional and complex, contributing to tumor metastasis and drug resistance. This study investigates the use of mRNA-based cancer agents as promising tools to combat and reverse refractory TIME conditions.

Methods

We optimized and engineered an mRNA cancer agent encoding double tandemly repeated sequences of the T cell costimulator Oxford 40 ligand (diOX40L). The diOX40L mRNAs were encapsulated into lipid nanoparticles (LNPs) for effective delivery. The research explored its safety and antitumor effects through a series of in vivo and in vivo experiments.

Results

Our results demonstrate that diOX40L mRNAs efficiently express increased levels of OX40L proteins. The optimized diOX40L mRNA cancer agent generated potent immune costimulatory signals within the TIME, leading to decreased tumor growth and improved survival compared to the original sequence agent. OX40L expression in subcutaneous tumors promoted CD4+ and CD8+ T cell activation, resulting in heightened IFN-γ and IL-2 secretion and robust immune responses. Combination therapy involving PD-1 antibodies and diOX40L substantially enhanced antitumor efficacy, with increased infiltration of activated CD4+ and CD8+ T cells.

Discussion

In conclusion, our findings highlight the therapeutic potential of the optimized diOX40L mRNA cancer agent in cancer treatment and its potential as an innovative alternative to protein-based therapies. The study underscores the significance of mRNA-based agents in modulating the immune microenvironment and enhancing antitumor responses.

miR-15a and miR-15b modulate natural killer and CD8+T-cell activation and anti-tumor immune response by targeting PD-L1 in neuroblastoma

Neuroblastoma (NB) is an enigmatic and deadliest pediatric cancer to treat. The major obstacles to the effective immunotherapy treatments in NB are defective immune cells and the immune evasion tactics deployed by the tumor cells and the stromal microenvironment. Nervous system development during embryonic and pediatric stages is critically mediated by non-coding RNAs such as micro RNAs (miR). Hence, we explored the role of miRs in anti-tumor immune response via a range of data-driven workflows and in vitro & in vivo experiments. Using the TARGET, NB patient dataset (n=249), we applied the robust bioinformatic workflows incorporating differential expression, co-expression, survival, heatmaps, and box plots. We initially demonstrated the role of miR-15a-5p (miR-15a) and miR-15b-5p (miR-15b) as tumor suppressors, followed by their negative association with stromal cell percentages and a statistically significant negative regulation of T and natural killer (NK) cell signature genes, especially CD274 (PD-L1) in stromal-low patient subsets. The NB phase-specific expression of the miR-15a/miR-15b-PD-L1 axis was further corroborated using the PDX (n=24) dataset. We demonstrated miR-15a/miR-15b mediated degradation of PD-L1 mRNA through its interaction with the 3'-untranslated region and the RNA-induced silencing complex using sequence-specific luciferase activity and Ago2 RNA immunoprecipitation assays. In addition, we established miR-15a/miR-15b induced CD8+T and NK cell activation and cytotoxicity against NB in vitro. Moreover, injection of murine cells expressing miR-15a reduced tumor size, tumor vasculature and enhanced the activation and infiltration of CD8+T and NK cells into the tumors in vivo. We further established that blocking the surface PD-L1 using an anti-PD-L1 antibody rescued miR-15a/miR-15b induced CD8+T and NK cell-mediated anti-tumor responses. These findings demonstrate that miR-15a and miR-15b induce an anti-tumor immune response by targeting PD-L1 in NB.

TIGIT/CD226 Axis Regulates Anti-Tumor Immunity

Tumors escape immune surveillance by inducing various immunosuppressive pathways, including the activation of inhibitory receptors on tumor-infiltrating T cells. While monoclonal antibodies (mAbs) blocking programmed cell death 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) have been approved for multiple cancer indications, only a subset of patients benefit from immune checkpoint blockade therapies, highlighting the need for additional approaches. Therefore, the identification of new target molecules acting in distinct or complementary pathways in monotherapy or combination therapy with PD-1/PD-L1 blockade is gaining immense interest. T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif (ITIM) domains (TIGIT) has received considerable attention in cancer immunotherapy. Recently, anti-TIGIT mAb (tiragolumab) has demonstrated promising clinical efficacy in non-small cell lung cancer treatment when combined with an anti-PD-L1 drug (Tecentriq), leading to phase III trial initiation. TIGIT is expressed mainly on T and natural killer cells; it functions as an inhibitory checkpoint receptor, thereby limiting adaptive and innate immunity. CD226 competes for binding with the same ligands with TIGIT but delivers a positive stimulatory signal to the immune cells. This review discusses the recent discoveries regarding the roles of TIGIT and CD226 in immune cell function and their potential application in cancer immunotherapy.